Increased aggression is commonly associated with many neurological and psychiatric disorders. Current treatments are largely empirical and are often accompanied by severe side effects, underscoring the need for a better understanding of the neural bases of aggression. Vasopressin, acting through its 1a receptor subtype, is known to affect aggressive behaviors. The vasopressin 1b receptor (Avpr1b) is also expressed in the brain, but has received much less attention due to a lack of specific drugs. Here we report that mice without the Avpr1b exhibit markedly reduced aggression and modestly impaired social recognition. By contrast, they perform normally in all the other behaviors that we have examined, such as sexual behavior, suggesting that reduced aggression and social memory are not simply the result of a global deficit in sensorimotor function or motivation. Fos-mapping within chemosensory responsive regions suggests that the behavioral deficits in Avpr1b knockout mice are not due to defects in detection and transmission of chemosensory signals to the brain. We suggest that Avpr1b antagonists could prove useful for treating aggressive behavior seen, for example, in dementias and traumatic brain injuries.

Two wildtype non-littermates were placed in the cage on the left and two Avpr1b knockout non-littermates in the cage on the right. The wildtype mice soon began to show aggressive signs, such as tail rattling, and were separated when they began to fight. The knockout mice in the other cage were watched for 45 minutes (a little over 3 minutes are shown here) and no aggressive behavior was observed.